I usually just phase door, or run to the nearest corridor and hide around a corner.They can't use their breath weapons on you that way, and your only fighting them one at a time.

That doesn't usually work very well with smart-packs enabled (the default). They won't come around a corner unless they think you are vulnerable to multiple attacks. You need to go around a corner into a room, and kill them instantly as they enter. But it only works if you can kill them in a single turn. If you have stone to mud or good tunneling, you can create a small room in an existing hallway; that's safer than using a full-sized room.

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With smart-packs and insufficient killing power, you probably need to run. Eventually you will outdistance your pursuers.

That doesn't usually work very well with smart-packs enabled (the default). They won't come around a corner unless they think you are vulnerable to multiple attacks.

They will also pursue you if you are sufficiently hurt. (The threshold seems to be about 50%.)

On very rare occasion I will step into a room of hounds, take a couple rounds of breaths, and then back into the hallway to finish them one by one. Light and dark hounds are good early candidates for this, earth hounds are okay later. Inertia hounds practically beg for it. Vague rule of thumb: you need to be able to take a dozen or two breaths safely, be able to kill a hound in a couple blows, and have a corner close to the room.

That doesn't usually work very well with smart-packs enabled (the default). They won't come around a corner unless they think you are vulnerable to multiple attacks.

True (although in V under 50% hp counts as vulnerable). Recall that you pretty much need ESP/telepathy to target smart packs intelligently: both near-misses from ball spells, and hockey-puck targeting, work in V. [They will not enter los, but will enter the hockey-puck projectability zone. Hockey-puck targeting obviously doesn't work in variants that have explicitly quashed such targeting.]